Patent GB-467467-A (GB)
Title: Improvements in telephone or like systems
IPC: H04Q1/442
Filed: 1935-12-16
Abstract: 467,467. Automatic exchange systems. AUTOMATIC ELECTRIC CO., Ltd., SAVILLE, W., and WILLIAMS, A. H. Dec. 16, 1935, No. 32561 /36. Divided out of 467,442. [Class40(iv)] In a system in which impulses are transmitted between exchanges in the form of A.C. at a commercial frequency, e.g. 50 cycles, mechanical impulse repeaters are employed at the points at which D.C. impulses are converted to A.C. and vice versa to enable A.C. impulses to be sent at a speed related to the frequency and D.C. impulses at a speed suitable for operating the switches. In the arrangements described, the register senders are of the mechanical regenerator type described in Specification 458,095. D.C.-A.C. repeater, Figs. 1 and 2. When the operator plugs in, A, B, BA, CC, CR pull up in turn, the lastnamed cutting off CC, BA. CC, CR control the sending of a temporary burst of 50-cycle current over the junction to prepare its incoming end. On the relapse of BA, which has been holding A to guard against false operation if the operator withdraws the plug immediately after plugging in, the operator is given control of A and, on hearing dialling tone from the distant exchange, dials or keys up the wanted number. Relay A repeats the digit to the receiving magnet MR of the regenerator and parallel dialling relay C. S is operated over the sleeve circuit, e.g. by dial off-normal springs, and holds the marking magnet MM operated until the end of the digit whereupon the magnet falls and displaces the selected pin. As soon as the receiving disc goes off normal, springs MN1 energize IP which operates IS and when the springs mm reclose at the end of the digit CC is reoperated to connect A.C. to the junction and shunt out IP. On the relapse of IS, which follows that of IP, the sending magnet MS is operated to push the displaced pin out of the path of the sending disc and open springs ms. IP, IS are then re-operated and MS falls to release the disc and cause the transmission of the first digit in the form of A.C. impulses by the springs IMP. After the transmission of the final digit, springs MNI re-open and relays CC, IP, IS are finally released. The reply signal takes the form of a burst of A.C. which operates AC whereupon CA locks and operates BA. When AC falls at the end. of the burst, CB pulls up to reverse the connections of the line relay and locks itself. Clearing by the called party causes a further burst of A.C. and this time AC energizes CD which locks itself and CB temporarily and cuts off CA. On the relapse of the last named relay, BA re-energizes to hold A until the end of the burst independently of the operator. AC, CB, CD, BA then fall back. If the calling party clears .first A and B fall and C and CC pull up temporarily to send a burst of A.C. forward to release the switches in the distant office. If the operator withdraws the plug prematurely, B is held operated and the busy lamps VES glow until the regenerator has been restored. A.C.-D.C. repeater, Figs. 3 and 4. Relay AC on receiving the seizing signal energizes A which is followed by B. B remains locked when AC, A fall at the end of the signal and the bridge across the outgoing circuit prepares the associated selector circuit. Rectifiers MRC, MRD polarize the bridged relays I, D in opposite directions, and at this stage I pulls up, energizing IX which locks, and D remains back. AC repeats the digits to A and to the receiving magnet MR and at the first impulse of each, C, DX pull up in series and the marking magnet MM is operated. When the regenerator goes off normal IP, IS pull up and at the end of the first digit the relapse of C and consequent release of MM and closure of mm energize BY which locks up and shunts out IP which releases IS to operate the sending magnet MS. This removes the shunt from IP which releases MS to release the sending disc which controls the transmission of DC. impulses at springs IMP. When all digits have been sent, BY, IP, IS fall back. When the called party replies, I falls and D pulls up, followed by E, DR. DE operates sluggishly and cuts off E which during its operation connects AC. to the incoming junction. DR also releases DX. When the calling party hangs up AC responds to the clearing signal and is followed by A and C, which shunt out B to release the switches. At the end of the signal AC, A and C fall back. If the called party clears first, D falls and I is operated again, and E and ER pull up in series energizing DR which brings down E, ER. While E is energized an A.C. signal is sent back over the junction. Fault alarms. If the regenerator in either repeater fails to re-transmit all the stored digits a delayed alarm is operated.